24 TUFTS COLLEGE STUDIES, VOL. IV, No. 7 



Page 135, for Key to the Species of Volvox, substitute, 



I. Colonies ovoid ; antbeiidia arranged in spheres, without vegetntive 



cells. i. /'. spermatosphata. 



i. Colonies spherical. 2. 



2. Colonies 600-1500/1 diam. 3. 



2. Colonies 200-500 M diaui. 4. 



3. Monoecious; antherozoids in free flat disks. 4. I', globular. 



3. Dioecious ; antherozoids in hollow spheres, becoming flattened. 



5. V. pcrglobator. 

 4. Colonies 350 500 M diam. ; reproductive bodies 8-10, in 2 or 3 planes. 



2. V. Wcissmanniana. 



\. Colonies about 200 M diam. ; reproductive bodies in varying numU T . 

 not originating in any definite order. 3. V. aurcus. 



1. V. SPERMATOSPHARA Powers, 1908, p. 142, PI. XXIII, 



XXIV; 1907, PI. XI-XIII. Colonies distinctly ovoid ; cells with 

 stigmas abundant at anterior pole, decreasing in number towards 

 posterior pole ; no strands of protoplasm connecting cells : ma- 

 ture colonies 1 50- looo /A diam., commonly 250-600 /*, containing 

 1000-3000 cells; parthenogonidia, oospores and male colonies 

 in varying proportions in the same colony, 1-25 in all, average 

 8 ; parthenogonidia ovoid, about 200 ^ diam. ; oospores 40-50 M 

 diam., with smooth wall ; " sperm spheres " spherical, ioo-i2Ofi 

 diam., containing 64,128 or 256 disks, usually 32 antherozoids 

 in each ; sperm spheres without distinction between poles, with 

 vegetative cells, breaking up while in the mother colony. 

 Neb., Mo. 



2. V. WKISSMANNIANA Powers, 1908, p. 152, PI. XXV. 

 XXVI. Colonies spherical, poles differentiated; cytoplasmic 

 threads distinct ; mature colonies 350-500 /* diam. ; i>aithem> 

 gonidia, oogonia and male colonies in varying proportions in 

 same mother cell, usually 8, arising in two plains, sometimes 

 10. the two additional in another plane ; parthenogonidia 150 

 170/4 diam. ; oospores 40-50 n diam., with smooth wall; male 

 colonies spherical, 200-250 M diam., containing numerous anthe- 

 ridia, curved disks, of 64 or 128 antherozoids each. Mo. 



3. V. AUREUS Ehrenberg, 1832, p. 77; 1838, p. 71, PI. IV, 

 fig. 2. Proterogynous ; colonies about 200 p. diam., of 600-900 

 cells with cytoplasmic connections; vegetative cells 4-6.5 /* 

 diam.; oogonia 1-15, 50-60 ft. diam., membrane smooth; anthe- 

 ridia numerous, small. 16 or 32 cells each, united in small 

 daughter colonies, with vegetative cells. Europe. 



No American citations or localities are given for this species 

 or for V. globator as it is probable that much of the material 



